The present invention relates in general to harvesting of living vessels for use in grafting, and, more specifically, to a harvesting device for endoscopically removing a vessel and a surrounding pedicle of fat and connective tissue using ferromagnetic heating to cut and cauterize tissue.
Blood vessels are often dissected from one portion of a living body to be implanted in another portion of the body by a surgical procedure, such as in a coronary artery bypass graft (CABG) or other cardiovascular procedure. An artery or vein is “harvested” (i.e., removed) from its natural location in a patient's body and reconnected to provide blood circulation elsewhere in the body. Among the preferred sources for the vessels to be used as the bypass graft are the saphenous vein in the leg and the radial artery in the arm.
Endoscopic surgical procedures for harvesting a section of a blood vessel (e.g., the saphenous vein) subcutaneously have been developed in order to avoid disadvantages and potential complications of harvesting of the blood vessel by exposing the desired vein section externally through a continuous incision along the leg. The continuous incision for exposing the vein and for introducing the surgical instruments to seal and sever adjoining tissue and side branches of the vessel results in a significant healing process and associated risks.
The known minimally-invasive endoscopic techniques employ a small incision for locating the desired vessel and for introducing one or more endoscopic devices into the small incision. For example, typical commercially available products for performing the endoscopic blood vessel harvesting procedure include a number of separate endoscopic devices that are each inserted into the patient. These endoscopic devices include, for example, an insufflation mechanism having plastic tubing to supply air or CO2 to insufflate the subcutaneous area; an endoscope having a camera and light cables in order to visualize both the dissection and harvesting procedures; a dissector mechanism to dissect or separate the vessel from connective tissues in the body (i.e., blunt dissection); and a cutting mechanism to sever and seal any side branches from the vessel and then remove the vessel from the body (i.e., active cutting). In certain instances, the combination of mechanisms can be bulky and cumbersome for the clinician performing the vessel harvesting. Also, in certain instances, these mechanisms require that a relatively large diameter wound and cavity be formed within the patient in order to accommodate all the separate mechanisms.
Existing harvesting devices have required an intricate and physically demanding procedure to isolate a vessel from surrounding tissue and to cut and coagulate side branches. This required a high level of skill and practice for the person performing the harvesting procedure. Even with good expertise, several potential sources of damage to the harvested vessel remain. Harvesting typically requires multiple passes of one or more separate devices resulting in much contact with the vessel, potentially leading to endothelial damage. To create a sufficient working space and to allow visualization for tissue separation and side branch cutting, significant insufflation is often used. The CO2 insufflation gas can lead to tissue acidosis, CO2 embolism, and other complications. The common use of electrocauterization for cutting and coagulating the side branches can result in thermal spreading to the harvested vessel and sometimes also results in side branch stubs that are too short for obtaining a good, leak-proof seal. Moreover, the delivery of RF electrical energy is bipolar (i.e., requires separate grounding of tissue) which can be undesirable.
It has been discovered that improved patency can be obtained for a vein graft if some surrounding tissue is left intact around the desired vessel. To address the absence of endoscopic devices capable of maintaining a layer of surrounding tissue (i.e., a pedicle) over the harvested vessel, copending U.S. application Ser. No. 14/021,537, filed Sep. 9, 2013, entitled “Single-Pass Endoscopic Vessel Harvesting” discloses a ring-shaped blade mounted to a sheath and disposed in a plane substantially perpendicular to the longitudinal direction and proximal of a dissector tip. The blade forms a lateral loop to encircle the vessel from the flanking tunnel and to make a vasiform cut including a pedicle around the vessel as the sheath advances. The disclosure of application Ser. No. 14/021,537 is incorporated herein by reference.
To reduce some disadvantages that may be associated with electrocauterization or other cutting methods, ferromagnetic heating can be used on a cutting surface to generate a controlled heating, as shown in co-pending U.S. application Ser. No. 14/926,305, filed Oct. 29, 2015, entitled “Single-Pass Endoscopic Vessel Harvesting” which is also incorporated herein by reference. Appropriate ferromagnetic materials and the generation of energizing signals can be as disclosed in U.S. Pat. No. 8,292,879.